The positive effects of fucoidans extracted from the brown seaweed Saccharina japonica on protection against CCl4-induced liver injury

Fucoidan is a sulphated polysaccharide derived from brown algae that contains a variety of bioactive compounds. The brown alga Saccharina japonica is an abundant bioresource for the commercialization of fucoidan, which has been aquacultured on a large scale in China. To explore the hepatoprotective effect of fucoidans from S. japonica, the seaweeds were extracted using an enzymolysis protocol, and a crude extract (F) was obtained by ethanol precipitation. Then, F was subjected to diethylaminoethyl (DEAE) column chromatography, and three fractions (F1, F2, and F3) were collected. The fundamental characteristics, including the monosaccharide composition and the structural features of F1–F3, were investigated using high-performance liquid chromatography (HPLC), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopy. F1 and F2 were rich in galactose and mannuronic acid, respectively, in addition to containing fucose. F3 mainly consisted of sulphated fucopyranose. All three fractions showed in vitro antioxidative activity against the hydroxyl radical. The hepatoprotective activities of F1–F3 were evaluated. Mice were orally administered fucoidans for 1 week and then intraperitoneally injected with CCl₄. Four hepatoprotective indicators were analysed to evaluate the efficacy of the three preparations. A high dose of F3 (300–500 mg kg⁻¹ day⁻¹) caused a significant difference in all four indicators compared to the control without fucoidan; this result was confirmed by histological examination of the mouse liver tissues. These results suggest that fucoidans from S. japonica had potential as ingredients for functional foods or pharmaceuticals to prevent liver injury.